In recent years, a Large Scale Integration (LSI) on which an analog circuit, a memory, an integrated circuit, and the like are mixedly mounted on one chip is commercialized as a System on a Chip (SoC).
As the memory mounted on the LSI, for example, a Static Random Access Memory (RAM) is mainly used, but in recent years, it is considered to use a semiconductor storage element, such as a Dynamic RAM (DRAM), a Magnetic RAM (MRAM), or a Ferroelectric RAM (FeRAM), for reducing cost and power consumption.
Here, the FeRAM is a semiconductor storage element that stores information in a direction of residual polarization of the ferroelectric that can control a direction of polarization depending on an external electric field. As a structure of the FeRAM, for example, a one-Transistor-one-Capacitor (1T1C)-type structure that uses a capacitor including a ferroelectric material, as a storage element, a one-Transistor (1T)-type structure that uses, as a storage element, a field effect transistor that uses a ferroelectric material in a gate insulator film, and the like are proposed.
Nevertheless, because a plurality of storage elements share word lines and bit lines in the FeRAM of the 1T-type structure, in the case of writing information thereinto, voltage is applied not only to a selected storage element, but also to an unselected storage element that shares the word lines and the bit lines. Thus, there has been a possibility that, by writing information into the selected storage element, information stored in the unselected storage element is rewritten.
For example, Patent Literature 1 described below discloses individually controlling voltage to be applied to word lines and bit lines of a selected storage element, and voltage to be applied to word lines and bit lines of an unselected storage element, when writing information into the selected storage element.
Specifically, Patent Literature 1 discloses applying voltage of Vcc to the word lines and the bit lines of the selected storage element, and applying voltage of ⅔ Vcc or ⅓ Vcc to the word lines and the bit lines of the unselected storage, when writing information. According to the technology disclosed in Patent Literature 1, while applying voltage equal to or larger than a threshold value that can reverse a polarization direction, only to a gate insulator film of the selected storage element, voltage to be applied to a gate insulator film of the unselected storage element can be suppressed to voltage less than the threshold value.